KVM: x86: Convert TSC writes to TSC offset writes

Change svm / vmx to be the same internally and write TSC offset
instead of bare TSC in helper functions.  Isolated as a single
patch to contain code movement.

Signed-off-by: Zachary Amsden <zamsden@redhat.com>
Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>

2 files changed, 22 insertions, 20 deletions

diff --git a/arch/x86/kvm/svm.c b/arch/x86/kvm/svm.c
index af5b9ea51965..e06f00d1f15c 100644
--- a/arch/x86/kvm/svm.c
+++ b/arch/x86/kvm/svm.c
@@ -701,6 +701,20 @@ static void init_sys_seg(struct vmcb_seg *seg, uint32_t type)
         seg->base = 0;
 }
 
+static void svm_write_tsc_offset(struct kvm_vcpu *vcpu, u64 offset)
+{
+        struct vcpu_svm *svm = to_svm(vcpu);
+        u64 g_tsc_offset = 0;
+
+        if (is_nested(svm)) {
+                g_tsc_offset = svm->vmcb->control.tsc_offset -
+                               svm->nested.hsave->control.tsc_offset;
+                svm->nested.hsave->control.tsc_offset = offset;
+        }
+
+        svm->vmcb->control.tsc_offset = offset + g_tsc_offset;
+}
+
 static void init_vmcb(struct vcpu_svm *svm)
 {
         struct vmcb_control_area *control = &svm->vmcb->control;
@@ -901,7 +915,7 @@ static struct kvm_vcpu *svm_create_vcpu(struct kvm *kvm, unsigned int id)
         svm->vmcb_pa = page_to_pfn(page) << PAGE_SHIFT;
         svm->asid_generation = 0;
         init_vmcb(svm);
-        svm->vmcb->control.tsc_offset = 0-native_read_tsc();
+        svm_write_tsc_offset(&svm->vcpu, 0-native_read_tsc());
 
         err = fx_init(&svm->vcpu);
         if (err)
@@ -2566,20 +2580,9 @@ static int svm_set_msr(struct kvm_vcpu *vcpu, unsigned ecx, u64 data)
         struct vcpu_svm *svm = to_svm(vcpu);
 
         switch (ecx) {
-        case MSR_IA32_TSC: {
-                u64 tsc_offset = data - native_read_tsc();
-                u64 g_tsc_offset = 0;
-
-                if (is_nested(svm)) {
-                        g_tsc_offset = svm->vmcb->control.tsc_offset -
-                                       svm->nested.hsave->control.tsc_offset;
-                        svm->nested.hsave->control.tsc_offset = tsc_offset;
-                }
-
-                svm->vmcb->control.tsc_offset = tsc_offset + g_tsc_offset;
-
+        case MSR_IA32_TSC:
+                svm_write_tsc_offset(vcpu, data - native_read_tsc());
                 break;
-        }
         case MSR_STAR:
                 svm->vmcb->save.star = data;
                 break;
diff --git a/arch/x86/kvm/vmx.c b/arch/x86/kvm/vmx.c
index 4fbab2469bf9..d9bec5ee38b8 100644
--- a/arch/x86/kvm/vmx.c
+++ b/arch/x86/kvm/vmx.c
@@ -1149,9 +1149,9 @@ static u64 guest_read_tsc(void)
  * writes 'guest_tsc' into guest's timestamp counter "register"
  * guest_tsc = host_tsc + tsc_offset ==> tsc_offset = guest_tsc - host_tsc
  */
-static void guest_write_tsc(u64 guest_tsc, u64 host_tsc)
+static void vmx_write_tsc_offset(u64 offset)
 {
-        vmcs_write64(TSC_OFFSET, guest_tsc - host_tsc);
+        vmcs_write64(TSC_OFFSET, offset);
 }
 
 /*
@@ -1255,7 +1255,7 @@ static int vmx_set_msr(struct kvm_vcpu *vcpu, u32 msr_index, u64 data)
                 break;
         case MSR_IA32_TSC:
                 rdtscll(host_tsc);
-                guest_write_tsc(data, host_tsc);
+                vmx_write_tsc_offset(data - host_tsc);
                 break;
         case MSR_IA32_CR_PAT:
                 if (vmcs_config.vmentry_ctrl & VM_ENTRY_LOAD_IA32_PAT) {
@@ -2512,7 +2512,7 @@ static int vmx_vcpu_setup(struct vcpu_vmx *vmx)
 {
         u32 host_sysenter_cs, msr_low, msr_high;
         u32 junk;
-        u64 host_pat, tsc_this;
+        u64 host_pat;
         unsigned long a;
         struct desc_ptr dt;
         int i;
@@ -2653,8 +2653,7 @@ static int vmx_vcpu_setup(struct vcpu_vmx *vmx)
                 vmx->vcpu.arch.cr4_guest_owned_bits |= X86_CR4_PGE;
         vmcs_writel(CR4_GUEST_HOST_MASK, ~vmx->vcpu.arch.cr4_guest_owned_bits);
 
-        tsc_this = native_read_tsc();
-        guest_write_tsc(0, tsc_this);
+        vmx_write_tsc_offset(0-native_read_tsc());
 
         return 0;
 }